SHiller made his name on that latter piece and I think it is still hotly debated. I think broadly the likely answer is 'yes' (ie too volatile to be justified by fundamentals).

Complicating factor as we saw this crisis is the level and performance of the stock market directly drives the ability of the financial stocks to pay dividends, thus a positive feedback loop (both up and down) which is not self correcting. Similar for the Real Estate sector.

Also for the home finance and home construction sector. The housing bubble drove those stocks. Just as during the dot com bubble, the stocks of HP, IBM, Cisco, Sun, Intel, Verizon etc were driven up by inflated demand for tech hardware, software and services. So when the stock prices fell, so did the markets for their kit, thus lowering earnings, and 'torpedo stock' lowering PEs as well-- so double whammy down.

These built in positive feedback loops between the financial markets and the companies listed on them increases their instability. Just as the Loan-to-Value lending metric for Commercial RE increases the bubble-bust behaviour of that sector-- ie causing increased leverage at the top, and reducing leverage at the bottom.